External Ophthalmoplegia and Brainstem White Matter Lesions: Presentation of Myotonic Dystrophy Type 1

Myotonic dystrophy type 1 (DM1) is an autosomal dominant condition which phenotype can be extremely variable considering its multisystem involvement, including the central nervous system. Neuromuscular findings are facial and distal extremities muscle weakness, muscle atrophy and myotonia. Standard diagnosis is obtained with molecular testing to detect CTG expansions in the myotonic dystrophy protein of the kinase gene. Brain magnetic resonance imaging typically shows characteristic subcortical white matter (WM) abnormalities located within anterior temporal lobes.

We present a 39-year-old male patient with a progressive external ophthalmoplegia, facial and limb muscle weakness, percussion myotonia and atypical brain magnetic resonance imaging findings, showing confluent brainstem WM lesions, affecting the pons, a rare radiologic feature in this disorder. Genetic testing confirmed the diagnosis for DM1.

This presentation with external ophthalmoplegia and brainstem WM loss in DM1 can show an important correlation with clinical findings and have an important diagnostic and prognostic value.